A double-blinded, randomized trial comparing surgeon-administered transversus abdominis plane block with placebo after midline laparotomy in gynecologic oncology surgery
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BACKGROUND: Surgeon-administered transversus abdominis plane block is a contemporary approach to providing postoperative analgesia, and this approach is performed by transperitoneally administering local anesthetic in the plane between the internal oblique and transversus abdominis muscles to target the sensory nerves of the anterolateral abdominal wall. Although this technique is used in many centers, it has not been studied prospectively in patients undergoing a midline laparotomy. OBJECTIVE: This study aimed to evaluate whether surgeon-administered transversus abdominis plane block reduces postoperative opioid requirements and improves clinical outcomes. STUDY DESIGN: In this double-blind, randomized, placebo-controlled trial, patients with a suspected or proven gynecologic malignancy undergoing surgery through a midline laparotomy at 1 Canadian tertiary academic center were randomized to either the bupivacaine group (surgeon-administered transversus abdominis plane blocks with 40 mL of 0.25% bupivacaine) or the placebo group (surgeon-administered transversus abdominis plane blocks with 40 mL of normal saline solution) before fascial closure. The primary outcome was the total dose of opioids (in morphine milligram equivalents) received in the first 24 hours after surgery. The secondary outcomes included opioid doses between 24 and 48 hours, pain scores, postoperative nausea and vomiting, incidence of clinical ileus, time to flatus, and hospital length of stay. The exclusion criteria included contraindications to study medication, history of chronic opioid use, significant adhesions on the anterior abdominal wall preventing access to the injection site, concurrent nonabdominal surgical procedure, and the planned use of neuraxial anesthesia or analgesia. To detect a 20% decrease in opioid requirements with a 2-sided type 1 error of 5% and power of 80%, a sample size of 36 patients per group was calculated. RESULTS: From October 2020 to November 2021, 38 patients were randomized to the bupivacaine arm, and 41 patients were randomized to the placebo arm. The mean age was 60 years, and the mean body mass index was 29.3. A supraumbilical incision was used in 30 of 79 cases (38.0%), and bowel resection was performed in 10 of 79 cases (12.7%). Patient and surgical characteristics were evenly distributed. The patients in the bupivacaine group required 98.0±59.2 morphine milligram equivalents in the first 24 hours after surgery, whereas the patients in the placebo group required 100.8±44.0 morphine milligram equivalents (P=.85). The mean pain score at 4 hours after surgery was 3.1±2.4 (0-10 scale) in the intervention group vs 3.1±2.0 in the placebo group (P=.93). Clinically significant nausea or vomiting was reported in 1 of 38 patients (2.6%) in the intervention group vs 1 of 41 patients (2.4%) in the placebo group (P=.95). Time to first flatus, rates of clinical ileus, and length of stay were similar between groups. Subgroup analysis of patients with a body mass index of <25 and patients who received an infraumbilical incision showed similarly comparable outcomes. CONCLUSION: Surgeon-administered transversus abdominis plane block with bupivacaine was not found to be superior to the placebo intervention in reducing postoperative opioid requirements or improving other postoperative outcomes for patients undergoing a midline laparotomy. These results differed from previous reports evaluating the ultrasound-guided transversus abdominis plane block approach. Surgeon-administered transversus abdominis plane block should not be considered standard of care in postoperative multimodal analgesia.
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